1. Field of the Invention
The present invention relates to holders for discharge lamps and particularly to such holders for fluorescent lamps having heat emissive electrical components contained within a portion of a bi-pin lamp base which is inserted into the holder for normal lamp operation.
Public and industry concern regarding energy conservation has led to the development of energy efficient discharge lamps such as the PL* brand of bi-pin fluorescent lamps sold by North American Philips Lighting Corporation. These lamps have a design which includes only one base and a generally U- shaped tubular glass envelope whose two parallel tubular portions are both mounted, at one end, on the base. Typically, the base is a unitary part formed of a suitable plastic. At the end opposite the base end, the tubular portions are welded together to provide fluid communication between them. Typically, the lamp includes a pair of filaments disposed within the two gas-filled tubular portions which also contain the fluorescent material. The lamp base is generally T-shaped and includes an elongate hollow trunk portion formed with an opposed pair of upper branch portions extending from the trunk. Metal wiring electrically connects the filament pair to electrical components disposed within the trunk cavity and to a respective pair of parallel opposed contact pins provided on and extending from the branches. The cavity-disposed components typically include part of a pre-heat and ballast circuit. Such components are in close proximity to each other and also to the lamp filaments. The lamp pins allow the electrical connection of such components to other components external of the lamp. These external conponents include the remainder of the ballast circuit and the power source.
2. Description of the Prior Art
For normal lamp operation, the trunk of the lamp base is received into a holder including a plastic housing having a lamp base receiving recess formed by the inside surfaces of two pairs of opposed housing walls and a floor. The contact pins of a received lamp are electrically engaged by a respective pair of opposed conductors suitably disposed within the holder. The holder disposed conductors are electrically connected by wires to the remainder of the ballast circuit external of the holder. More importantly, the housing walls and floor inside surfaces are all interconnected such that they each have close dimensional tolerances with the received lamp trunk. Further, the known holder has no effective fluid communication between the trunk-receiving recess and the ambient atmosphere outside of the holder. These known lamp holders, therefore, have not proven entirely satisfactory, because of overheating.
During operation, the power dissipation within the lamp contained circuit components causes the components disposed within the lamp base cavity to emit heat. This heat emission is increased by the cavity-disposed components' close proximity to the hot operating lamp filaments. This heat is transferred to the lamp base whose temperature, therefore, rises.
However, because of the close dimensional tolerances between the heated lamp base and the housing walls/floor and also because of the ineffective heat dissipation to the ambient atmosphere (the plastic housing is a relatively poor heat conductor), the known holders cause the component-emitted heat to be substantially retained within the lamp base and the immediately adjacent spaces between the base and the housing. Such heat retention is energy inefficient for lamp operation and may adversely affect overall lamp and/or holder life.